Allenic aldehydes



United States Patent 3,225,102 ALLENIC ALDEHYDES Benjamin Thompson,Kingsport, Tenn., assignor to Eastman Kodak Company, Rochester, N.Y., acorporation of New Jersey No Drawing. Filed Dec. 13, 1960, Ser. No.75,475 13 Claims. (Cl. 260-598) This application is acontinuation-in-part of my US. application, Serial No. 861,750, filedDecember 24, 1959, and now abandoned, entitled, Allenic Aldehydes andProcess of Manufacturing Them.

This invention relates to compounds having two adjacent carbon-carbondouble bonds such as are found in allene, and to a process for makingthem. More specifically, it relates to compounds having the functionalgroup,

The basic reaction of my process is believed to be a fundamentally newdiscovery and is applicable to a wide range of different aldehyde andacetylenic alcohol starting materials. I have demonstrated the reactionmost extensively in preparing novel 3,4-dienaldehydes of the formula:

wherein R and R are alkyl groups or cycloalkyl groups; and R R and R arehydrogen or alkyl or cycloalkyl groups. The reaction by which aldehydesof the above formula are prepared in accordance with my invention isbelieved to proceed through the formation of an intermediate enol ethertype of compound which rearranges to the allenic aldehyde form, asillus- Although I do not wish to be bound by theoretical explanations ofthe results I have obtained, all of the reactions in accordance with theinvention that I have observed are consistent with the formation of anenol ether intermediate. The postulated equation above thereforeprovides a means for defining the aldehydes that can be used. Thus, Ihave found that only aldehydes of two or more carbon atoms per moleculethat are capable of forming an enol ether with an acetylenic alcohol asin the equation will produce the novel allenic aldehydes.

Aldehydes suitable for the reaction have at least two carbon atoms permolecule. In the broadest aspect R 'ice and R of the aldehyde in theabove equation can be hydrogen or various radicals, including alkyl,cycloalkyl, alkaryl, alkenyl or other substituents that will notinterfere with the reaction of the aldehyde and acetylenic alcohol informing the enol ether and the propargylic rearrangement to the allenicaldehyde.

The principal aldehydes suitable for the reaction are aldehydes of atleast four carbon atoms that have a single hydrogen atom on the alphacarbon atom. If the aldehyde has two hydrogen atoms on the alpha carbonatom the rearrangement reaction can take place twice, yielding adiallenic substituted aldehyde which is easily lost by polymerization orcondensation reactions.

Aldehydes having no hydrogen atom on the alpha carbon are suitable ifthere is available elsewhere in the molecule a hydrogen atom that can besplit off in forming the postulated enol ether intermediate. However,the most important class of aldehydes are the aldehydes having onehydrogen atom on the alpha carbon atom. Examples include 2-alkylaliphatic aldehydes such as isobutyraldehyde, Z-methylbutyraldehyde,2-ethylbutyraldehyde, Z-ethylpentanaldehyde, 2- methylhexanaldehyde,2-ethylhexanaldehyde, 2-methylpentanaldehyde,2-ethyl-4-methylpentanaldehyde, 2,4- dimethylpentanal; and cyclicaldehydes such as oyclohexanecarboxaldehyde, cyclopentanecarboxaldehyde,and norbornanecarboxaldehyde. Thus, the cyclic aldehydes includealdehydes in which R and R are alkylene groups which, together with thealpha carbon atom to which they are attached, form a carbocyclic ring.

The acetylenic alcohols suitable for my process include propargylalcohol and substituted propargyl alcohols of the following structure:

wherein R R and R can be hydrogen, alkyl, cycloalkyl, alkaryl, alkenyl,or other non-interferring substituents. R and R can be alkylene groupsthat form a carbocyclic ring with the carbon to which they are attached.

Examples of suitable alcohols include propargyl alcohol; a-substitutedpropargyl alcohols in which R of the above formula is hydrogen and Rand. R are either hydrogen or lower alkyl groups, e:g.,3-methyl-1-pentyn- 3 ol, 3 methyl 1 butyn-3-ol, 1-hexyn-3-ol, 4-ethyl-1-octyn-3-ol, and 3-methyl-1-nonyne-3-ol; and a-substituted proparglalcohols in which R or R is a cycloalkyl substituent such as l-ethynylcyclohexanol, 1- ethynyl cyclopentanol, and2,2,6-trimethyl-l-ethynylcyclohexanol. Although acetylenic alcoholshaving substituents on both acetylenic carbon atoms, i.e., R is alkyl,cycloalkyl, etc., are scarce and expensive there is no reason that suchalcohols cannot be used satisfactorily in my process and thereforeallenic compounds prepared from such alcohols are within the scope ofthe invention.

I have found that 3,4-dien-1-als can be prepared by heating the selectedaldehyde with the propargyl alcohol or substituted propargyl alcohol inthe liquid phase in the presence of an acidic catalyst. Virtually anytype of acidic material will catalyze the reaction. Examples are:phosphoric acid, toluene-sulfonic acid, methionic acid, borontrifiuoride, acidic ion exchange resins, etc. The reaction will takeplace without the addition of any acid other than the trace amountswhich may be present in the aldahyde used. When lower aldehydes such asisobutyraldehyde are being reacted, it is helpful to increasethereaction temperature either by the use of moderately elevatedpressure or by the addition of a high boiling solvent such asdiisopropyl benzene, cymene, etc.

The reaction can also be carried out as a continuous vapor phase processin the presence of a solid catalyst. This procedure has the advantagethat secondary reactions can be minimized and the need for separatingthe acidic catalyst from the products is avoided. Catalysts includematerials such as silica gel, fullers earth, and activated carbon.Better results are obtained by impregnating such materials with acidiccompounds such as MnSO ZnSO CaCl Al (SO MgSO etc. Such impregnatingmaterials can include other materials that will impart acidity to thecatalyst such as acidic ions derived from phosphorous, arsenic,vanadium, tungsten, molybdenum and the like, either as free acid or insalt form.

Promoted catalysts as described above are conveniently prepared byimpregnation of the support with a solution or dispersion containingsuflicient acidic constituent to give a concentration of the promotingingredient of from about 0.1% to about 25% by weight of the catalystfollowing evaporation of the solvent.

The vapor phase reaction will take place at a tempera 'ture as low as125 C. but temperatures as high as about 450 C. can be used. Contacttimes vary inversely to the temperature and may be in the range of aboutone minute to a small fraction of a second.

My invention is illustrated but not limited by the following examples ofpreparation of allenic aldehydes:

Example 1.A solution of 280 g. (5 moles) of propargyl alcohol, 504 g. (7moles) of isobutyraldehyde, 1.0 g. of p-toluenesulfonic acid, and 200 g.of diisopropyl benzene was heated in a fractionating still having meansfor removing water at the head. 95 g. of water was removed over a periodof 30 hrs. The charge was then fractionated. More than 220 g. of2,2-dimethyl-penta- 3,4-dien-1-al was recovered. B.P. 131 C., 11 1.4531.Infrared analysis showed that there was no conjugated unsaturationpresent but that allenic unsaturation was present (absorption at 5.1microns). Nuclear magnetic resonance showed that there were the correctnumber and intensities of hydrogen protons present to agree with thestructure CH C CHC(CH CHO.

Analysis.-Theoretical: C, 76.32; H, 9.15; O, 14.53. Found: C, 75.85; H,9.19; O, 14.96. Carbonyl equivalent weight 111 (theory 110.15).Reduction of the product, resulting in its taking up 3 molecules ofhydrogen, gave 2,2-dirnethylpentanol, B.P. 156 C., n 1.4259.

Example 2.A solution of 1,720 g. of Z-methyl butyraldehyde, 1,120 g. ofpropargyl alcohol, 1 g. of methionic acid, 1 g. of hydroquinone, and 160cc. of benzene was boiled in a still topped by a reflux condenser andwater separator. After 360 cc. of water had separated, 1 g. of sodiumbicarbonate was added. Fractionation at atmospheric and reduced pressureseparated 2-ethyl-2- 'methyl-penta-3,4-dien-l-al, B.P. 92 C. at 100 mm.,

11 1.4603. Infrared analysis showed this aldehyde to have a strongabsorption at 5.1 microns, which. is characteristic of the C:C:Cstructure.

Example 3.-Substituting equal moles of 2-ethylhexanaldehyde forZ-methylbutyraldehyde in Example 2 produced2-butyl-2-ethyl-penta-3,4-dien-1-al, B.P. 210 C.

Example 4.Substituting Z-methyl-pentanaldehyde forZ-methyI-butyraldehyde in Example 2 produced Z-methyl-2-propyl-penta-3,4-dien-1-al, B.P. 175 C.

Example 5 .A solution of 740 g. of isobutyraldehyde, 981 g. of3-methyl-1-pentyn-3-ol, 1 g. of methionic acid and 100 ml. of benzenewas refluxed until 186 cc. of water separated at the head of the column.1 g. of sodium acetate and 0.1 g. of hydroquinone were added, and thecharge was fractionated to recover over 400 g. of2,2,5-trimethyl-hepta-3,4-dien-1-al, B.P. 99.5 C. at 52 mm., n 1.4580,and having a strong infrared absorption at 5.1 microns showing thepresence of the C:C:C

group.

Likewise, 3-methyl-1-butyn-3-ol gave 2,2,5-trimethylhexa-3,4-dien-l-al,B.P. 99 C. at 104 mm., n 1.4550.

Likewise, 1-hexyn-3-ol gave 2,2-dimethyl-octa-3,4-dien- 1-al, B.P. 8990C. at 22 mm., 11 1.45901.4595.

Likewise, 4-ethyl-1-octyn-3-ol gave 2,2-dimethyl-6-ethyl-deca-3,4-dien-1-al, B.P. 88 C. at 2.0 mm., n 1.46291.4632.

Likewise, 3-methyl-l-nonyne-3-ol gave2,2,5-trimethylundeca-3,4-dien1-al, B.P. 78 C. at 0.8 mm., 11 1.4607-1.4610.

Preparation of allenic aldehydes having cyclic substituents is shown bythe following examples:

Example 6.--Preparation of 3-butenaldehyde,4-cyclohexylidene-2,2-dimethyl: The following materials were charged toa still having means for decanting water that separates at the head:19.8 g. of l-ethynyl cyclohexanol, 230 g. of isobutyraldehyde, 10 g. ofbenzene, 0.1 g. of p-toluenesulfonic acid, and 0.3 g. of hydroquinone.This charge was refluxed rapidly under a nitrogen atmosphere until 32 g.of water layer separated at the head of the column. This required 74hrs. but may be shortened by increasing the catalyst concentration, etc.The product was then fractionated under vacuum to recover excessisobutyraldehyde, 27 g. of unreacted l-ethynyl cyclohexanol, 22.1 g. ofthe allenic aldehyde, 4-cyclohexylidene-2,2-dimethyl-3-butenaldehyde,having the formula:

B.P. 94 C. at 2.2 mm., 11 1.4915.

Analysis.NMR and infrared absorptions are in agreement with structure.Found: 80.59% C, 10.24% H (theory, 80.84% C, 10.18% H).

Likewise, l-ethynyl cyclopentanol has been reacted with isobutyraldehydeto prepare 4-cyclopentylidene-2,2- dimethyl-3-butenaldehyde, and withoher aldehydes to give similar allenic aldehydes.

Example 7.-Preparation of 2-norbornanecarboxaldehyde,3-methyl-2-propadienyl: Charge consisted of 1414 g. of2-norbornanecarboxaldehyde, 3-methyl, 168 g. of propargyl alcohol, 30 g.of benzene, and 0.5 g. of ptoluenesulfonic acid. The charge was refluxedin a still under a nitrogen atmosphere until 54 cc. of water had beendecanted at the head. Vacuum fractionation of the product gave mainlytwo isomers of 2-norbornanecarboxaldehyde, 3-methyl-2-propadienyl,having the formula B.P. 96 C. at 5.2 mm. and C. at 1.1 mm., n 1.5153 and1.5183. Infrared analysis confirmed the presence of the propadienylgroup in both.

Likewise, cyclohexane carboxaldehyde and cyclopentane carboxaldehydewere reacted with propargyl alcohol to produce the correspondingpropadienyl substituted aldehydes, 1-propadienylcyclohexanecarboxaldehyde and 1-propadienylcyclopentane carboxaldehyde.

Preparation of a 3-substituted 3,4-dienal from a substituted propargylalcohol in which R is a lower alkyl group is illustrated by the nextexample.

Example 8.A solution of 200 g. of 2-butyn-1-ol, 366 g. of 2-ethylhexanaldehyde, 0.1 g. hydroquinone, 0.15 g. of p-toluenesulfonic acidand 50 g. of benzene were refluxed in a still having means forseparating water at its head until 52 g. of water had separated.Fractionation of the charge under reduced pressure produced 273 g. of3,4-pentadienal, 2-butyl-2-ethyl-3methyl, B.P. 80 C. at 4 mm. Infraredshows the characteristics adsorption for C=C=C at 5.1 microns.

Although aldehydes having one hydrogen atom attached to the alpha carbonatom are the preferred reactants for my process, I have indicated thatthe reaction can be carried out with aldehydes having no hydrogen atomon the alpha carbon atom, provided that the aldehyde can rearrange by asimple double bond shift to a structure that will permit the enol etherto be formed. The following example demonstrates the reaction with ana,/3-unsaturated aldehyde which can rearrange to provide a hydrogen atomon the alpha carbon atom by a simple double bond shift.

Example 9.A solution of 294 g. of 3-methyl-1-pentyn- 3-ol, 384 g. of2-ethyl-2-hexenaldehyde, 0.15 g. of ptoluene sulfonic acid, 0.1 g. ofhydroquinone, 50 g. of benzene, and 25 g. of toluene were refluxed in astill, having means for separating water at the head, for 68 hours.During this time, when water separation slowed down, a total of 0.4 g.of the acid catalyst was added and 2.0 moles of water were separated.The catalyst was neutralized with NaHCO Fractionation of the crudeproduct isolated 185 g. of 3,4heptadienal, 2-(1-butenyl)-2-ethyl-S-methyl, B.P. 72 C. at 0.8 mm., n 1.4780-8. This represents a 69%yield based on the 33% of the 3- methyl-1-pentyn-3-ol not recovered inthe fractionation of products. Infrared and NMR analyses show that thel-butenyl group is the trans-isomer.

The use of another unsaturated aldehyde is demonstrated in the nextexample. aldehyde is tetrahydrobenzaldehyde, an aldehyde in which R andR together with the alpha carbon atom of the aldehyde, form acycloalkenyl radical.

Example 10.-A solution of 123 g. of tetrahydrobenzaldehyde, 65 g. ofpropargyl alcohol, 20 g. of p-xylene, 50 g. of benzene, and 0.1 g. ofp-toluene sulfonic acid was refluxed until 17 g. of water separated. Thebase temperature rose from 125 to 163 C. in this period. The catalystwas neturalized with sodium bicarbonate and the crude product wasfractionated. 25 g. of l-propadienyl tetrahydrobenzaldehyde product,B.P. 54i5 C. at 0.8 mm., 11 1.5120-30, was obtained. Infrared analysisconfirms the presence of the functional groups. Tetrahydrobenzaldehydedipropargyl acetal, B.P. 79 C. at 0.7 mm., 11 1.4910, was obtained as aby-product.

The synthesis of 3,4dienaldehydes as described in prior examples in somecases produces a 3,5-dienaldehyde byproduct. This very likely isproduced by isomerization of the 3,4-dienal. Its formation is enhancedby prolonged heating, higher catalyst concentrations, and reactiontemperatures. Example 11 describes a run from which a yield of the3,5-dienal was isolated.

Example 11.--A solution of 350 g. of 2-methyl-3- butyn-Z-ol, 222 g. ofisobutyraldehyde, 15 g. of benzene, and 0.3 g. of p-toluene sulfonicacid was refluxed in a still (as described in prior examples) for 64hours removing water at the still head. In this time the basetemperature rose from 80 to 140 C. The crude product was fractionated.In addition to 152 g. of 3,4-hexadienal-2,2,5- trimethyl, B.P. 83 C. at52 mm., n 1.4572, there was obtained 60 g. of3,5-hexadienal-2,2,5-trimethyl, B.P. 9597 C. at 52 mm., r1 1.471030, and18.5 g. of 1,2,4-trirnethylbenzene.

- Dienaldehydes can be prepared in accordance with the invention byheating the mixture of aldehyde and acetylenic alcohol under pressure at125-200 C. for several hours. This can be useful especially in acontinuous process. In one form of the process the solution of aldehyde,alcohol, catalyst, etc., is pumped into a tube heated to the reactiontemperature and of such length and volume as to provide the desiredreaction time, e.g., several minutes or hours. The liquid reactionproducts are continuously discharged at the other end of the tube into afractionating still where the aldehyde, water, and unreacted alcohol areseparated from the dienal and other products. The unreacted aldehyde andalcohol are recirculated. The dienaldehyde is isolated by furtherdistillation. One advantage of such a process is that it reduces theamount of heat required to carry out the reaction under refluxconditions.

Example 12 demonstrates the synthesis of dienals at elevated pressure,as developed autogenously in a heated autoclave.

Example 12.-A solution of 144 g. of isobutyraldehyde, 84 g. of propargylalcohol, 100 g. of p-xylene, 0.2 g. of hydroquinone, and 0.15 g. ofphosphoric acid was charged to an autoclave and heated for 8 hours at175 C. Analysis of products gave 9 g. of 2,2dimethyl -3,4-pentadienalrepresenting a 50% yield on the propargl alcohol that reacted. Heatingat 200 C. more than doubled the conversion to the dienal.

Vapor phase preparation of an allenic aldehyde is illustrated by thefollowing example:

Example Han-During a period of 3 hr., a mixture consisting of 173 g.(2.4 moles) of isobutyraldehyde, 67.3 g. (1.2 moles) of propargylalcohol, and 4.9 moles of nitrogen was passed over activated carbon(Carbide and Carbon Chemicals Corporation, Columbia Grade CXAL) at atemperature of 200 C. and a contact time of 19.2 seconds. (Contact timeis defined as the time in seconds that one volume of gaseous feed is incontact with an equal volume of catalyst at reaction conditions oftemperature and pressure.) The organic reaction product, 230 g., wascollected in traps cooled to 10 C. and C. Analysis of the organicproduct showed 0.1 mole of 2,2- dimethyl-3,4-pentadienal and 1.08 molesof unreacted propargyl alcohol corresponding to a conversion to the tdienal of 8.3% based on the alcohol fed and a yield of 83.4% based onthe alcohol consumed.

As I have indicated, my invention extends to the preparation ofderivatives of the allenic aldehydes prepared in accordance with theinvention, including allenic acids and allenic alcohols prepared fromsuch aldehydes as intermediates.

Examples of specific valuable allenic alcohols that can be prapared inaccordance with the invention include: 2,2 dimethylpenta 3,4 dienol;2,2,5 trimethylhepta- 3,4 dienol; 2 ethyl 2 methylpenta 3,4 dienol; 2methyl 2 propylpenta 3,4 dienol; 2 butyl- 2 ethylpena 3,4 dienol; 2,2,5trimethylhexa 3,4- dienol; 2 allenyl 3 methylbicyclo[2,2,1]heptanemethanol; 4 cyclohexyliden 2,2 dimethyl 3 butenol; 2,2 dimethylocta 3,4dienol; 2 butyl 2 ethyl- 5 met'hylhexa 3,4 dienol; 2 butyl 2 ethylocta-3,4 dienol; and the alcohols of other dienals as disclosed above.

The method of preparation of the alcohols comprises initially thepreparation of the allenic aldehyde by the propargylic rearrangementdescribed above. The aldehyde is then reduced to an allenic alcohol ofthe same number of carbon atoms without saturating the adjacent doublebonds. Methods for reduction of unsaturated aldehydes to alcohols areknown in the art. These include disproportionation, electrolyticreduction, use of nascent hydrogen prepared by the action of acids onmetals, use

of amalygams, lithium aluminum hydride, boron compounds, aluminumalkoxides as in Meerwein-Ponndorf Verley reduction, etc.

The following examples illustrate preparation of allenic alcohols inaccordance with the invention:

Example 13.-120 g. of sodium hydroxide in 50% aqueous solution wasslowly added to a solution of 110 g. of 2,2-dimethylpenta-3,4-dien-1-aland cc. of 37% formalin in 400 g. of methanol. After stirring at 60 C.for 2 hours, water was added and the methanol distilled. Benzeneextraction and fractionation produced over 100 g. of2,2-dimethyl-penta-3,4-dien-l-ol, B.P. 83 C. at 40 mm., n 1.47128.

Example 14.165 g. of 2,2-dimethylpenta-3,4-dienaldehyde and 500 g. ofmethanol were charged to a stirred vessel. 90 g. of sodium hydroxide wasadded over an hour while holding the temperature at 6065 C. The solutionwas agitated for 3 hours or until all aldehyde had reacted. 1,500 cc. ofwater were added and the methanol was removed by distillation. Thesolution was extracted with benzene to remove the alcohol completely.This solution was then fractionated to recover over 70 g. of an alcoholwhich has been identified as 2,2-dimethylpenta-3, 4 dienol. B.P. 8083 C.at 40 mm., n 1.4708i5. Acidification of the alkaline solution liberatedthe corresponding acid.

Example 15.-84 g. of potassium hydroxide was dissolved in 50 g. of waterand 250 g. of methanol and warmed to reflux in a vessel with anagitator. 152 g. of 2,2,5-trimethylhepta-3,4-dienal dissolved in 150 g.of methanol was fed in over an hour. Refluxing was continued until thealdehyde concentration was negligible. 1,500 g. of water was added andthe methanol was distilled oif. The 2,2,5-trimethylhepta-3,4-dienol wasthen either separated by steam or azeotropic distillation or byextraction using benzene. Redistillation produced over 65 g. of thealcohol. B.P. 94 C. at 16 mm. The presence of the allenic group wasestablished by infrared absorption at 5.1 microns.

I have also prepared allenic alcohols in accordance with the inventionby a hydrogen transfer reaction, which is preferred in some cases to theCannizzaro reaction described above. The method of preparation isillustrated by the following examples:

Example ]6.2,400 g. (40 moles) of dry isopropanal, 761 g. (5 moles) of2,2-dimethyl-3,4-octadienaldehyde, and 2 g. of hydrouquinone werecharged to a fractionating still. After heating to reflux under anitrogen atmosphere and checking to determine that there was no waterpresent, g. of Aluminum Ch-elate PEA1 was added as catalyst. (AluminumChelate PEA-1, a product of Harshaw Chemical Co., is a derivative ofaluminum isopropylate in which one isopropoxide group is replaced byethylacetoacetate.) The isopropanol was gradually oxidized to acetoneand the dienal reduced to its alcohol. The still takeofi was regulatedto 70 C. and the acetone was removed as it formed. 30 g. of additionalcatalyst Was added over the course of 8 hours. When acetone no longerseparated at the still head, the excess isopropanol was distilled ofl.The alcohol product, 2,2-dimethyloeta-3,4-dien-l-ol, was isolated in 82%yield by fractionation under reduced pressure,

r1 1.4721, B.P. 7475 C. at 1.21.3 mm.

Example 17.-2,2 dimethyl-6-ethyl-3,4-decadienaldehyde was reduced to2,2-dimethyl-6-ethy1deca-3,4-dienl-ol in the same manner as above, usinga similar excess of isopropanol. A 96.5% yield of the alcohol wasobtained, B.P. 105 C. at 1.1 mm. pressure, 11 1.4729.

Example 18.-To 800 g. (4.5 moles) of 2,2-dimethyl-4-cyclohexylidene-3-butenaldehyde, 3000 g. of dry isopropanol, and 2 g.of hydroquinone was added 22 g. of aluminum isopropoxide in 100 g. oftoluene. Upon heating in a fractionating still, acetone separated andwas removed at the head. Four and five-tenths moles of acetone wereremoved in 2 hr. and tests showed the aldehyde to be consumed. Afterdistilling oil the excess isopropanol, 734 g. of the product alcohol,2,2-dimethyl-4-cyclohexylidene-3-butenol, was obtained (90% yield), B.P.81 C. at 0.5 mm., 11 1.5031.

Example 19.In a manner similar to the preceding example,2,2,5-trimethyl-3,4-heptadienaldehyde was reduced to2,2,5-trimethyl-3,4-heptadienol, using excess isopropanol and aluminumisopropoxide as catalyst. In this case the catalyst salts were filteredfrom the crude alcohol. A 75% yield was obtained, B.P. 82 C. at 9 mm, 111.4712.

Example 20.2,2,5-trin1ethyl-3,4-undecadienol was prepared by theCannizzaro reaction from 2,2,5-trimethyl-3,4-u11decadienaldehyde. 832 g.(4 moles) was added to 320 g. of sodium hydroxide dissolved in 320 g. ofwater and 1000 g. of methanol and refluxed until the aldehyde was almostcompletely reacted. Methanol was partly distilled off and toluene wasadded to help separate the alcohol from the aqueous layer. Fractionationof the organic layer produced 408 g. of 96% pure alcohol, 11 1.4706.Analysis of the alcohol by nuclear magnetic resonance gave a pattern inagreement with its structure.

The hydrogen transfer reaction illustrated by the above examples may becarried out using a wide range of molar ratios of alcohol to 3,4-dienal.Naturally, at least 1 mole of alcohol is required per mole of aldehyde.If less is used the reaction will go until all of the alcohol isoxidized. In addition to the isopropanol shown, any alcohol that can beoxidized to form an aldehyde or ketone may be used (tertiary alcoholscannot be). Even alcohols whose aldehydes or ketones boil higher thanthe dienal can be used. In this case the reaction is carried to anequilibrium and worked up or else a continuous methyl esterificationapparatus is used so that the higher boiling aldehyde or ketone can beseparated from the reaction.

In addition to the aluminum isopropoxide and aluminum chelate PEA, shownin examples, other metal alkoxides such as lithium, sodium, potassium,magnesium, stannic, zirconium, titanium, etc. may be used. Likewise,other alcohols may be used to form the alkoxide.

Temperature of the reduction may be varied as convenient for separationof the ketone 0r aldehyde formed. If the temperature is over 150 C.isomerization of the 3,4-dienol to 3,5-dienol may take place. Where R orR is hydrogen, some isomerization to 2,4-dienols and/or dehydration toolefins may take place at reaction temperatures above 100 C.

In addition to the liquid phase hydrogen transfer method of reducing the3,4-dienaldehydes to 3,4-dienols, this reaction may be carried out inthe vapor phase under conditions essentially as described in US. Patent2,767,211.

The 3,4-dienaldehydes may be isomerized to the 3,5-

dienaldehydes or partially hydrogenated to the 3- or 4- olefinicaldehydes. All of these may be reduced by the described hydrogentransfer method by merely substituting these aldehydes for the3,4-dienaldehydes described in the examples on a mole for mole basis.

The allenic alcohols of the invention prepared as described above have anumber of important uses. Some of the alcohols and their esters havepleasant odors and can be used in the formulation of perfumes andflavors or as insect attractants in insecticides.

The allenic acids of the invention are also prepared from the allenicaldehydes obtained by the propargylic rearrangement. Examples of acidsthat can be prepared 1n accordance with the invention from such allenicaldehydes include: 2,2-dimethylpenta-3,4-dienoic acid; 2,2,5trimethylhepta 3,4 dienoic acid; 2 ethyl 2- methylpenta 3,4 dienoicacid; 2 methyl 2 propylpenta 3,4 dienoic acid; 2 butyl 2 ethylpenta 3,4-dienoic acid; 2,2,5 trimethylhexa 3,4 dienoic acid; 2- allenyl 3methylbicyclo [2,2,1]heptane 2 carboxylic acid; and 4 cyclohexyliden 2,2dimethyl 3 butenoic acid.

The acids are prepared by oxidizing the allenic aldehydes. Methods foroxidation of aldehydes to acids, either by use of oxidizing agents orcatalytically with air or oxygen are well known in the art. However, inthe present process care must be taken to avoid reaction of the doublebonds if monobasic acids are desired. Preparation of the acids bydisproportionation of the aldehyde, by an oxidizing agent andcatalytically with air are described in the following examples.

Preparation of acid by the Cannizzaro reaction Example 21.120 g. ofsodium hydroxide in 50% aqueous solution was slowly added to a solutionof 110 g. of 2,2-dimethyl-penta-3,4-dien-l-al in 500 cc. of methanol.After stirring at 60 C. for 2 hours, water was added and the allenicalcohol was extracted with benzene. Fractionation separated over 50 g.of 2,2-dimethyl-penta- 3 ,4-dien-1-ol, B.P. 83 C. at 40 mm., 111.47l2i5. Acidification of the alkaline solution with acid, followed bybenzene extraction and distillation, gave over 50 g. of2,2-dimethylpenta-3,4-dienoic acid, B.P. 67-70" C. at 1.0-1.1 mm., n1.4669.

Example 22.-84 g. of potassium hydroxide was dissolved in 50 g. of waterand 250 g. of methanol and warmed to reflux in a vessel with anagitator. 152 g. of 2,2,S-trimethylhepta-3,4-dienaldehyde dissolved in150 g. of methanol was fed in over a 1-hour period. Refluxing wascontinued until aldehyde concentration was negligible. 1500 cc. of waterwas added and most of the methanol was distilled off. The byprodcct2,2,5-trimethylhepta- 3,4-dienal was then either separated by steam orazeotropic distillation, or extracted and then recovered. In either caseall non-acidic products were separated from the alkaline solution byextraction. The alkaline salt solution was then acidified with sulfuricacid. The 2,2,5- trimethylhepta-3,4-dienoic acid was separated andwashed and fractionated to recover 77 g. of acid. Acid purified byredistillation had the following properties: neut. equiv. 169.5; theory168.2; mol. wt. 170; B.P. 80-85 C. at 0.8 mm. Infrared confirmed astrong absorption characteristic of the C=@C structure at 5.1 microns.

Preparation of acid by use of an oxidizing agent Example 23.A suspensionof silver oxide was prepared by precipitating it from 340 g. of silvernitrate in 2 liters of water with 80 g. of sodium hydroxide in a vesselhaving agitation. The alkalinity was adjusted to pH of 11. One mole, 110g., of 2,2-dimethylpenta-3,4- dienal was slowly fed into the slurry overa 6-hour period holding the temperature below 25 C. During this time thealkalinity of the slurry was maintained at pH 10-12 by the gradualaddition of dilute sodium hydroxide. The slurry was held at pH 12 untilthe reaction was complete and all the aldehyde had been oxidized. Thesalt was filtered from the silver. The solution was extracted withbenzene to remove any organic byproducts as impurities. It was thenacidified using excess sulfuric acid. The dienoic acid was separated,the last being extracted with benzene, and fractionated to recover 115g. of 2,2- dimethylpenta-3,4-dienoic acid; B.P. 57 C. at 0.5 mm.pressure, neut. equiv. 126.8. Analyzing: C, 67.03%, H, 8.12% (theory: C,66.67%, H, 7.94%). Infrared analysis confirmed the presence of an -CC=C- group by a strong absorption at 5.1 microns.

Likewise, 2,2 dimethylocta 3,4 dienal gave 2,2 dimethylocta-3,4-dienoicacid, B.P. 97 C. at 0.8 mm., n 1.4694.

Likewise, Z-butyl-Z-ethyl--methylhexa3,4-dienal gave2-butyl-2-ethyl-S-methylhexa-3,4-dienoic acid, B.P. 110- 125 C. at0.6-1.0 mm. All three of these acids show absorption at 5.1 microns byinfrared, thus confirming the presence of the allene group.

Preparation of acid by catalytic oxidation Example 24.A half gram ofcobalt acetate hydrate was dissolved in 200 g. of acetic acid. Thissolution was placed in a 1" x 5' glass column provided with means todisperse air into its base and surmounted by a condenser. 5 cc. ofacetaldehyde were dissolved in the above solution and then a slow streamof air containing 9 g. of acetaldehyde vapor per cubic foot wasdispersed through it. The temperature rose and after -30 minutes thesolution took on the characteristic dark green color of an activeoxidation catalyst. At this point 2,2-dimethylpenta-3,4-dienal was fedinto the tower near its base at the rate of 11 g. per cubic foot of air(containing acetaldehyde) passed into the tower. The temperature washeld between 15 and 50 C. by cooling. After 220 g. ofdimethylpentadienal had been reacted, the flow of air was discontinuedand the solution was gradually warmed to C. over 4 hr. to slowlydecompose peroxy compounds. It was then cooled and treated with ferroussulfate until the peroxygen content was negligible. 400 g. of xylenewere added and the acetic acid was distilled off under low vacuum. Theremaining acid was converted to its sodium salt using 10% sodiumhydroxide. The organic byproducts were extracted from the aqueous saltsolution. This was then acidified to pH 2, the liberated acid extractedwith xylene and fractionated under vacuum. A 15% yield of acid, B.P. 55C. at 0.5 mm. was obtained.

The allenic acids prepared in accordance with the invention as describedabove have many important uses. They are principally useful asintermediates in the preparation of valuable derivatives such as estersand salts. Thus, esters of a number of the allneic acids have pleasantodors and are useful in the formulation of flavorsand perfumes. Themetal salts of these acids, such as the lead, cobalt or manganese salts,are useful as paint driers.

Preparation of a valuable derivative of an allenic acid in accordancewith the invention is described in the following example, suchderivative also aiding in identifying the structure of the acid.

Example 25. Dibromo-Z,Z-dimethylpentenoic acid.-A solution of bromine incarbon tetrachloride was added to a 20% solution of2,2-dimethylpenta-3,4-dienoic acid in carbon tetrachloride at 25 C.until the solution maintained the characteristic bromine color. The C01was evaporated and the residue was recrystallized from heptane. Thedibromo acid had the following analysis: B.P. 117-121 C.; neut. equiv.283.1 (286 theory); C, 28.95%; H, 3.70%; O, 10.91%; Br 55.47% (Theory:29.37%, 3.50%, 11.19% and 55.94%, respectively). Infrared confirmedpositively the presence of C C and --COOH.

A surprising result of the above example is that a dibromo rather than atetrabromo derivative was obtained. Thus, the allenic acids of theinvention can be reacted with a halogen such as bromide to obtain ahalogenated unsaturated acid, the latter being useful as an intermediatein production of further substituted mono-elofinic acids and acidderivatives.

As compounds of the invention, and as the aldehydes and acetylenicalcohols from which they are prepared, in which R R R and R are definedin the claims hereinafter as cycloalkyl radicals, I means to includecompounds in which either R and R or R and R or both of such pairs, arealkylene groups that form a carbocyclic ring with the carbon atom towhich they are attached.

The invention has been described in considerable detail with particularreference to certain preferred embodiments thereof, but it will beunderstood that variations and modifications can be effected within thespirit and scope of the invention as described hereinabove, and asdefined in the appended claims.

I claim: 1. Allenic alehydes of the formula \C=C=(|3(|1OHH I R5 32wherein R represents a member selected from the group consisting oflower alkyl radicals and lower alkenyl radicals, R represents loweralkyl radicals and wherein R and R together with the alpha carbon atomto which they are attached can be a member selected from the groupconsisting of cyclopentyl, cyclohexyl, cyclohexenyl and norboranayl, R Rand R each represents a member selected from the group consisting ofhydrogen and lower a-lkyl radicals and wherein R and R together with thecarbon atom to which they are attached can be a member selected from thegroup consisting of cyclopentyl, cyclohexyl and lower alkyl substitutedcyclohexyl radicals.

2. A 2,2-dialkyl-alka-3,4-dien-l-al having the formula wherein R and Rare lower alkyl radicals.

5. The compound 2,2-dimethyl-penta-3,4-dien-l-al. 6. The compound2-ethyl-2-methy1-penta-3,4-dien-1-al. '7. The compound2-butyI-Z-ethyl-penta-3,4-dien-1-al. 8. The compound2-methyl-2-propyl-penta-3,4-dienl-al.

9. The compound 2,2,5 -trimethyl-hepta-3,4-dien-l-al. 10. The compound4- cyclohexylidene-2,2-dimethyl-3- butenaldehyde.

12 11. The compound 3 -methyl-Z-propadienyl-2norbornanecarboxaldehyde.

12. The compound 2 (1 butenyl) 2-ethyl-5-methyl- 3,4-heptadienal.

13. The compound 2,Z-dimethyl-octa-3,4-dien-1-al.

References Cited by the Examiner UNITED STATES PATENTS 2,407,508 9/1946Morris et al 260598 X 2,410,007 10/1946 Bludworth et a1. 260--6172,435,403 2/1948 Morris et al 260598 X 2,497,349 2/1950 Farkas et al260617 2,515,595 7/1950 Geyer et al 260526 2,563,325 8/1951 Fahnoe260-615 X 2,568,635 9/1951 Jansen et al. 260 526 2,746,993 5/1956 Dean260-598 2,819,312 1/1958 Isler et al 260-598 2,947,786 8/1960 Brannock260615 X 2,957,028 10/1960 Brannock et al 260601 3,507,888 10/1962Marbet et al 260601 X FOREIGN PATENTS 203,474 5/1959 Austria. 719,45012/1954 Great Britain.

OTHER REFERENCES Brannock, Jour. Amer. Chem. Soc., vol. 81, July 17,1959, pages 3379-3383.

LEON ZITVER, Primary Examiner.

CHARLES B. PARKER, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,225,102 December 21, 1965 Benjamin Thompson It is hereby, certifiedthat error appears in the above numbered patent requiring correction andthat the said Letters Patent should read as corrected below.

Column 10, line 65, for "alehydes" read aldehydes lines 66 to 69, theformula should appear as shown below instead of as in the patent:

R Signed and sealed this 27th day of December 1966.

CHO

( Attest:

ERNEST W. SWIDER Attesting Offioer EDWARD J. BRENNER Commissioner ofPatents

1. ALLENIC ALEHYDES OF THE FORMULA